Phase locked loop (pll)-less millimeter wave power head

ABSTRACT

Embodiments of the disclosure relate to a phase locked loop (PLL)-less millimeter wave (mmWave) power head. The mmWave power head receives a multiplexed signal including a pilot signal at a base frequency and a communication signal at the IF frequency. The mmWave power head separates the pilot signal from the communication signal and multiplies the pilot signal to generate a local oscillator (LO) clock signal(s) at a harmonic frequency(ies) relative to the base frequency of the pilot signal. A selected LO clock signal is provided to a mixer circuit(s) for up and down conversions between the IF frequency and the mmWave carrier frequency. By eliminating the PLL frequency synthesizer from the mmWave power head, it is possible to avoid spur and coupling issues associated with collocating the PLL frequency synthesizer with an antenna front end module (FEM), thus helping to improve reliability and performance of the mmWave power head.

RELATED APPLICATIONS

This application claims the benefit of provisional patent applicationSer. No. 62/376,118, filed Aug. 17, 2016, the disclosure of which ishereby incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The technology of the disclosure relates generally to a modem and aradio frequency (RF) front end module (FEM) for supporting millimeterwave (mmWave) communications.

BACKGROUND

Mobile communication devices have become increasingly common in currentsociety for providing wireless communication services. The prevalence ofthese mobile communication devices is driven in part by the manyfunctions that are now enabled on such devices. Increased processingcapabilities in such devices means that mobile communication deviceshave evolved from being pure communication tools into sophisticatedmobile multimedia centers that enable enhanced user experiences.

A fifth-generation (5G) new radio (NR) (5G-NR) wireless communicationsystem has been widely regarded as the next wireless communicationstandard beyond the current third-generation (3G) communicationstandard, such as wideband code division multiple access (WCDMA), andfourth-generation (4G) communication standard, such as long-termevolution (LTE). The 5G-NR wireless communication system is expected toprovide a significantly higher data rate, improved coverage range,enhanced signaling efficiency, and reduced latency compared to wirelesscommunication systems based on the 3G and 4G communication standards.Moreover, the 5G-NR communication system is an orthogonal frequencydivision multiplexing (OFDM) based wireless system designed to operateacross a wide range of radio frequency (RF) bands.

The United States Federal Communications Commission (FCC) published aNotice of Inquiry (NOI) in October 2014 seeking comments on several RFbands as potential RF bands for the 5G-NR communication system. The RFbands under FCC consideration include 24 GHz bands (24.25-24.45 GHz and25.05-25.25 GHz), Local Multipoint Distribution Service (LMDS) bands(27.5-28.35 GHz, 29.1-29.25 GHz, and 31-31.3 GHz), 39 GHz bands (38.6-40GHz), 37/42 GHz bands (37.0-38.6 GHz and 42.0-42.5 GHz), 60 GHz bands(57-64 GHz and 64-71 GHz), and 70/80 GHz bands (71-76 GHz, 81-86 GHz,and 92-95 GHz). In this regard, a 5G-NR RF baseband and front end systemmay be required to operate effectively across a broad millimeter wave(mmWave) spectrum.

SUMMARY

Embodiments of the disclosure relate to a phase locked loop (PLL)-lessmillimeter wave (mmWave) power head. In examples discussed herein, thePLL-less mmWave power head is configured to support up and downconversions between an intermediate frequency (IF) and a mmWave carrierfrequency without requiring a PLL frequency synthesizer. Specifically,the mmWave power head receives a multiplexed signal including acommunication signal at the IF frequency and a pilot signal at a basefrequency higher than a crystal oscillator (XTAL) reference frequency.The mmWave power head separates the pilot signal from the communicationsignal and multiplies the pilot signal to generate a local oscillator(LO) clock signal(s) at a harmonic frequency(ies) relative to the basefrequency of the pilot signal. A selected LO clock signal is provided toa mixer circuit(s) for up and down conversions between the IF frequencyand the mmWave carrier frequency. By eliminating the PLL frequencysynthesizer from the mmWave power head, it is possible to avoid spur andcoupling issues associated with collocating the PLL frequencysynthesizer with an antenna front end module (FEM), thus helping toimprove reliability and performance of the mmWave power head.

In one aspect, an mmWave power head is provided. The mmWave power headincludes a signal input coupled to a wired communication medium andconfigured to receive a multiplexed signal comprising a communicationsignal at an IF frequency and a pilot signal at a base frequency. ThemmWave power head also includes filter circuitry coupled to the signalinput and configured to demultiplex the multiplexed signal to separatethe communication signal and the pilot signal. The mmWave power headalso includes one or more multiplication paths configured to multiplythe pilot signal to generate one or more LO clock signals at one or moreharmonic frequencies relative to the base frequency of the pilot signal,respectively. The mmWave power head also includes at least one mixercircuit coupled to a selected multiplication path among the one or moremultiplication paths and configured to upconvert the communicationsignal from the IF frequency to a mmWave carrier frequency base on aselected LO clock signal generated by the selected multiplication path.

In another aspect, a modem system is provided. The modem system includesan RF baseband circuit. The modem system also includes a plurality ofmmWave power heads coupled to the RF baseband circuit via a plurality ofwired communication mediums, respectively. Each mmWave power head amongthe plurality of mmWave power heads includes a signal input coupled to awired communication medium among the plurality of wired communicationmediums and configured to receive a multiplexed signal comprising acommunication signal at an IF frequency and a pilot signal at a basefrequency. Each mmWave power head among the plurality of mmWave powerheads also includes filter circuitry coupled to the signal input andconfigured to demultiplex the multiplexed signal to separate thecommunication signal and the pilot signal. Each mmWave power head amongthe plurality of mmWave power heads also includes one or moremultiplication paths configured to multiply the pilot signal to generateone or more LO clock signals at one or more harmonic frequenciesrelative to the base frequency of the pilot signal, respectively. EachmmWave power head among the plurality of mmWave power heads alsoincludes at least one mixer circuit coupled to a selected multiplicationpath among the one or more multiplication paths and configured toupconvert the communication signal from the IF frequency to a mmWavecarrier frequency base on a selected LO clock signal generated by theselected multiplication path.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1A is a schematic diagram of an exemplary modem system including aconventional transceiver circuit that relies on a phase locked loop(PLL) to generate a local oscillator (LO) clock signal for converting acommunication signal from an IF frequency to a millimeter wave (mmWave)carrier frequency for transmission via an antenna array.

FIG. 1B is a graph providing an exemplary frequency plan for combiningvarious signals into a multiplexed signal in the modem system of FIG.1A;

FIG. 2 is a schematic diagram of an exemplary modem system in which ammWave power head is configured to convert a communication signalbetween an IF frequency and a mmWave carrier frequency without requiringa PLL frequency synthesizer being provided in the mmWave power head;

FIG. 3 is a graph providing an exemplary frequency plan for combining acommunication signal, a pilot signal, and a control signal into amultiplexed signal in the modem system of FIG. 2;

FIG. 4 is a schematic diagram providing an exemplary illustration ofinner structure of one or more multiplication paths for generating oneor more local oscillator (LO) clock signals in the mmWave power head ofFIG. 2;

FIG. 5 is a schematic diagram of the mmWave power head of FIG. 2configured to support mmWave beamforming;

FIG. 6 is a schematic diagram of an exemplary modem system configured tosupport multiple mmWave RF front end subsystems by employing more thanone of the mmWave power head of FIG. 2; and

FIG. 7 is a schematic diagram of an exemplary base station employingmore than one of the modem system of FIG. 6.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element such as a layer, region, orsubstrate is referred to as being “on” or extending “onto” anotherelement, it can be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present.Likewise, it will be understood that when an element such as a layer,region, or substrate is referred to as being “over” or extending “over”another element, it can be directly over or extend directly over theother element or intervening elements may also be present. In contrast,when an element is referred to as being “directly over” or extending“directly over” another element, there are no intervening elementspresent. It will also be understood that when an element is referred toas being “connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “vertical” may be used herein to describe a relationshipof one element, layer, or region to another element, layer, or region asillustrated in the

Figures. It will be understood that these terms and those discussedabove are intended to encompass different orientations of the device inaddition to the orientation depicted in the Figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including” when used herein specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

Embodiments of the disclosure relate to a phase locked loop (PLL)-lessmillimeter wave (mmWave) power head. In examples discussed herein, thePLL-less mmWave power head is configured to support up and downconversions between an intermediate frequency (IF) and a mmWave carrierfrequency without requiring a PLL frequency synthesizer. Specifically,the mmWave power head receives a multiplexed signal including acommunication signal at the IF frequency and a pilot signal at a basefrequency higher than a crystal oscillator (XTAL) reference frequency.The mmWave power head separates the pilot signal from the communicationsignal and multiplies the pilot signal to generate a local oscillator(LO) clock signal(s) at a harmonic frequency(es) relative to the basefrequency of the pilot signal. A selected LO clock signal is provided toa mixer circuit(s) for up and down conversions between the IF frequencyand the mmWave carrier frequency. By eliminating the PLL frequencysynthesizer from the mmWave power head, it is possible to avoid spur andcoupling issues associated with collocating the PLL frequencysynthesizer with an antenna front end module (FEM), thus helping toimprove reliability and performance of the mmWave power head.

Herein, the mmWave refers to an electromagnetic spectrum (e.g., 24.25-95GHz) allocated to a fifth-generation new radio (5G-NR) communicationsystem(s). Accordingly, a mmWave carrier frequency refers to a radiofrequency (RF) band(s) that falls within the electromagnetic spectrum ofthe 5G-NR communication system(s). The term 5G-NR refers to a wirelesscommunication technology defined by the third-generation partnershipproject (3GPP) in long-term evolution (LTE) Release 15 (Rel-15) andbeyond.

Before discussing exemplary aspects of a PLL-less mmWave power head, abrief overview of a conventional transceiver circuit that relies on aPLL frequency synthesizer to generate an LO clock signal for frequencyconversion is first provided with references to FIGS. 1A and 1B. Thediscussion of specific exemplary aspects of a PLL-less mmWave power headstarts below with reference to FIG. 3.

FIG. 1A is a schematic diagram of an exemplary modem system 10 includinga conventional transceiver circuit 12 that relies on a PLL frequencysynthesizer 14 to generate a local oscillator (LO) clock signal forconverting a communication signal 16 from an IF frequency to a mmWavecarrier frequency for transmission via an antenna array 18. As it iswell known in the field of wireless communications, a conversion fromthe lower IF frequency to the higher mmWave carrier frequency can becarried out by a mixer circuit base on the LO clock signal. For example,to upconvert an 8.4 GHz IF frequency to a 48 MHz mmWave carrierfrequency, the LO clock signal can be provided either at 41.6 GHzfrequency for a low-side injection frequency conversion or at 56.4 GHzfrequency for a high-side injection frequency conversion. The LO clocksignal is generated by the PLL frequency synthesizer 14 based on acrystal oscillator (XTAL) reference clock 20 that is typically runningat a frequency below 300 MHz.

The conventional transceiver circuit 12 is coupled to a baseband circuit22 via a coaxial cable 24. The baseband circuit 22 includes a crystaloscillator 26 for generating the XTAL reference clock 20. In addition,the baseband circuit 22 is configured to receive and process a basebandsignal 28 to generate the communication signal 16. Further, the basebandcircuit 22 also generates a control signal 30 to control theconventional transceiver circuit 12 to transmit the communication signal16 via the antenna array 18. In this regard, the baseband circuit 22 isrequired to provide the communication signal 16, the XTAL referenceclock 20, and the control signal 30 to the conventional transceivercircuit 12 concurrently via the coaxial cable 24. Hence, the basebandcircuit 22 needs to multiplex the communication signal 16, the XTALreference clock 20, and the control signal 30 into a multiplexed signal32 for distribution to the conventional transceiver circuit 12concurrently over the coaxial cable 24.

To be able to unambiguously separate the communication signal 16, theXTAL reference clock 20, and the control signal 30 at the conventionaltransceiver circuit 12, the communication signal 16, the XTAL referenceclock 20, and the control signal 30 need to be added to the multiplexedsignal 32 based on different frequencies. In this regard, FIG. 1B is agraph providing an exemplary frequency plan 34 for combining thecommunication signal 16, the XTAL reference clock 20, and the controlsignal 30 into the multiplexed signal 32 in the modem system 10 of FIG.1A.

As mentioned earlier in FIG. 1A, the XTAL reference clock 20 istypically slower than 300 MHz. As such, the XTAL reference clock 20needs to be located closer to a zero Hz direct current (DC) frequency,such as 270 MHz as shown in FIG. 1B. However, the control signal 30 maybe originally generated in the same frequency range as the XTALreference clock 20. As such, the control signal 30 must be upshiftedfrom its original frequency to another frequency higher than the 270 MHzfrequency occupied by the XTAL reference clock 20. For example, as shownin FIG. 1B, the control signal 30 is upshifted to a 2.16 GHz frequency.The communication signal 16, which is located at a 8.64 GHz IFfrequency, is spatially separated from the XTAL reference clock 20 andthe control signal 30. Thus, by allocating the XTAL reference clock 20,the control signal 30, and the communication signal 16 at 270 MHz, 2.16GHz, and 8.64 GHz frequencies, respectively, the conventionaltransceiver circuit 12 would be able to separate the XTAL referenceclock 20, the control signal 30, and the communication signal 16 at 270MHz from the multiplexed signal 32. Subsequently, the conventionaltransceiver circuit 12 may downshift the control signal 30 back to theoriginal frequency.

However, upshifting the control signal 30 at the baseband circuit 22 anddownshifting the control signal 30 at the conventional transceivercircuit 12 can add significant processing complexity and overheads tothe modem system 10. In addition, collocating the PLL frequencysynthesizer 14 with the antenna array 18 can lead to significant spurand coupling issues that may compromise the accuracy of the LO clocksignal. Since the PLL frequency synthesizer 14 is configured to providephase correction to the LO clock signal based on a closed-loop feedbackof the LO clock signal, the PLL frequency synthesizer 14 may potentiallyboost phase noise of the LO clock signal. For example, if the LO clocksignal is at 28 GHz and the XTAL reference clock 20 is at 10 MHz, thePLL frequency synthesizer 14 can introduce approximately 70 dB of phasenoise to the LO clock signal, thus compromising accuracy of the LO clocksignal. Furthermore, the PLL frequency synthesizer 14 may generateadditional heat, which can make heat dissipation a more challenging taskin the modem system 10. As such, it may be desirable to overcome thedeficiencies of the conventional transceiver circuit 12 by eliminatingthe PLL frequency synthesizer 14.

In this regard, FIG. 2 is a schematic diagram of an exemplary modemsystem 36 in which a mmWave power head 38 is configured to convert acommunication signal 40 between an IF frequency F_(IF) and a mmWavecarrier frequency F_(C) without requiring a PLL frequency synthesizerbeing provided in the mmWave power head 38. As such, the mmWave powerhead 38 is also referred to as a PLL-less mmWave power head. Byeliminating the PLL frequency synthesizer (e.g., the PLL frequencysynthesizer 14 of FIG. 1A) from the mmWave power head 38, the mmWavepower head 38 will not need the XTAL reference clock 20 of FIG. 1A. As aresult, it is no longer necessary to upshift the control signal 30 tomake room for the XTAL reference clock 20 in the frequency plan 34 ofFIG. 1B. Therefore, it is possible to reduce the processing complexityand overhead associated with upshifting and downshifting the controlsignal 30, thus making the modem system 36 more efficient. Further, byeliminating the PLL frequency synthesizer from the mmWave power head 38,it is possible to avoid the spur and coupling issues as well as heatdissipation challenges associated with collocating the PLL frequencysyntheisizer with the

RF FEM, thus allowing the modem system 36 to operate with improvedreliability and efficiency.

As is further discussed below, the mmWave power head 38 receives andmultiplies a pilot signal 42, which is at a base frequency F_(B) atleast ten times higher than the XTAL reference clock 20 of FIG. 1A, togenerate one or more LO clock signals 44(1)-44(N) at one or moreharmonic frequencies F_(H1)-F_(HN) relative to the base frequency F_(B).A selected LO clock signal 46, which can be any of the LO clock signals44(1)-44(N), is chosen to provide a selected LO reference frequencyF_(LO) for use by at least one mixer circuit 48 to upconvert thecommunication signal 40 to generate a mmWave RF signal 49 at the mmWavecarrier frequency F_(C). In this regard, it is possible to plan andcontrol the harmonic frequencies F_(H1)-F_(HN) by adjusting the basefrequency F_(B) of the pilot signal 42. Further, it is possible todetermine the base frequency F_(B) based on the mmWave carrier frequencyF_(C). Thus, by selecting a proper base frequency F_(B), it is possiblefor the mmWave power head 38 to generate the LO clock signals44(1)-44(N) at the harmonic frequencies F_(H1)-F_(HN) to upconvert thecommunication signal 40 to a wide range of the mmWave carrier frequencyF_(C).

In a non-limiting example, Table 1 below provides an exemplary summaryof a spectral range of the mmWave carrier frequency F_(C), to which thecommunication signal 40 having the IF frequency F_(IF) between 3.2-4.2GHz can be upconverted based on the pilot signal 42 at the basefrequency F_(B) between 6.4-8.4 GHz.

TABLE 1 N U F_(IF) (GHz) F_(B) (GHz) F_(LO) (GHz) F_(C) (GHz) 1 03.2-4.2 6.4-8.4 6.4-8.4 6.4-8.4 3 1 19.2-25.2 22.4-29.4 5 −1 32.0-42.028.8-37.8 5 1 35.2-46.2 7 −1 44.8-58.8 41.6-54.6 7 1 48.0-63.0 9 −157.6-75.6 54.4-71.4 9 1 60.8-79.8

In Table 1, N represents an order of harmonics, and U represent ahigh-side injection (1) and a low-side injection (−1). For example, inthe row where N=3 and U=1, the selected LO clock signal 46 provides theselected LO reference frequency F_(LO) that equals the 3^(rd) orderharmonic frequency (19.2-25.2 GHz) relative to the base frequency F_(B).Accordingly, the mixer circuit 48 can upconvert the communication signal40 from the IF frequency F_(IF) (3.2-4.2 GHz) to the mmWave carrierfrequency F_(C) between 22.4 GHz (=19.2 GHz +3.2 GHz) and 29.4 GHz(=25.2 GHz +4.2 GHz). As shown in Table 1, by generating the selected LOclock signal 46 between the 3^(rd) order harmonic frequency and the9^(th) order harmonic frequency relative to the base frequency F_(B),the communication signal 40 can be upconverted to the mmWave carrierfrequency FC that ranges from 22.4 GHz to 79.8 GHz.

The mmWave power head 38 includes a signal input 50 coupled to an RFbaseband circuit 52 via a wired communication medium 54. In anon-limiting example, the wired communication medium 54 is a singlecoaxial cable for providing interconnection between the RF basebandcircuit 52 and the mmWave power head 38. The mmWave power head 38receives a multiplexed signal 56, which includes the communicationsignal 40 at the IF frequency F_(IF) and the pilot signal 42 at the basefrequency F_(B), via the signal input 50. The mmWave power head 38includes filter circuitry 58, which is coupled to the signal input 50,configured to receive and demultiplex the multiplexed signal 56 toseparate the communication signal 40 and the pilot signal 42. The mmWavepower head 38 includes one or more multiplication paths 60(1)-60(N)configured to multiply the pilot signal 42 to generate the LO clocksignals 44(1)-44(N) at the harmonic frequencies F_(H1)-F_(HN),respectively. The selected LO clock signal 46, which herein refers tothe LO clock signal 44(1) at the harmonic frequency F_(H1) as anon-limiting example, is routed to the mixer circuit 48 to provide theselected LO reference frequency F_(LO) for upconverting thecommunication signal 40 from the IF frequency F_(IF) to the mmWavecarrier frequency F_(C). Notably, the selected LO clock signal 46 canalso be utilized by the mixer circuit 48 for downconverting thecommunication signal 40 from the mmWave carrier frequency F_(C) to theIF frequency F_(IF).

In a non-limiting example, the filter circuitry 58 includes a firstfilter 62 and a second filter 64, which can be acoustic filters such assurface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters,and/or film bulk acoustic resonator (FNAR) filters for example. Thefirst filter 62 can be a bandpass filter configured to pass thecommunication signal 40 at the IF frequency F_(IF) and reject the pilotsignal 42 at the base frequency F_(B). The second filter 64 can be abandpass filter configured to pass the pilot signal 42 at the basefrequency F_(B) and reject the communication signal 40 at the IFfrequency F_(F). As such, the first filter 62 and the second filter 64can effectively separate the pilot signal 42 from the communicationsignal 40.

In another non-limiting example, each of the multiplication paths60(1)-60(N) can include a clock multiplier 66 and a bandpass filter 68.The clock multiplier 66 is configured to multiply the pilot signal 42 togenerate a respective LO clock signal among the LO clock signals44(1)-44(N) at a respective harmonic frequency among the harmonicfrequencies F_(H1)-F_(HN). For example, the clock multiplier 66 in themultiplication path 60(1) multiplies the pilot signal 42 to generate theLO clock signal 44(1) at the harmonic frequency F_(H1), and the clockmultiplier 66 in the multiplication path 60(N) multiplies the pilotsignal 42 to generate the LO clock signal 44(N) at the harmonicfrequency F_(HN). The bandpass filter 68, which may be implemented by atransmission line filter, is configured to pass the respective LO clocksignal while rejecting noises associated with the respective LO clocksignal. In other words, the bandpass filter 68 smoothes out therespective LO clock signal by removing the spurs in the respective LOclock signal.

The multiplexed signal 56 can also include a control signal 70 at afrequency F_(CTRL) that is below 300 MHz. In this regard, the filtercircuitry 58 may include a third filter 72, which can be a lowpassfilter to pass the control signal 70 while rejecting the communicationsignal 40 and the pilot signal 42. The communication signal 40, thepilot signal 42, and the control signal 70 can be multiplexed at the RFbaseband circuit 52 and demultiplexed at the mmWave power head 38 basedon a frequency plan as discussed next in FIG. 3.

In this regard, FIG. 3 is a graph providing an exemplary frequency plan74 for combining the communication signal 40, the pilot signal 42, andthe control signal 70 into the multiplexed signal 56 in the modem system36 of FIG. 2. Common elements between FIGS. 2 and 3 are shown thereinwith common element numbers and will not be re-described herein.

As previously discussed, the base frequency F_(B) of the pilot signal 42is at least ten times higher than the XTAL reference clock at afrequency below 300 MHz. As such, the frequency F_(CTRL) of the controlsignal 70 can be located close to the DC frequency, without beingupshifted as in the modem system 10 of FIG. 1A. As shown in FIG. 3, thefrequency F_(CTRL) of the control signal 70, the IF frequency F_(IF) ofthe communication signal 40, and the base frequency F_(B) of the pilotsignal 42 are non-overlapping with each other.

Notably, there can be third-generation (3G) and/or fourth-generation(4G) cellular bands 76, residing between the frequency F_(CTRL) and theIF frequency F_(F). As such, to avoid overlapping with the 3G/4Gcellular bands 76, the selected multiplication path can be configured togenerate the selected LO reference frequency F_(LO) higher than themmWave carrier frequency F_(C). As such, the mmWave RF signal 49 can begenerated based on a high-side injection of the selected LO clock signal46, thus helping to avoid unintended overlapping with the 3G/4G cellularbands 76.

With reference back to FIG. 2, the RF baseband circuit 52 incudes abaseband IC 78 and a multiplexer/demultiplexer circuit 80. The basebandIC 78 includes a baseband circuit 82 and a PLL frequency synthesizer 84configured to generate the communication signal 40 and the pilot signal42, respectively. The pilot signal 42 may be amplified by an amplifier86 prior to being provided to the multiplexer/demultiplexer circuit 80.The multiplexer/demultiplexer circuit 80 multiplexes the communicationsignal 40 and the pilot signal 42 to generate the multiplexed signal 56.The RF baseband circuit 52 then provides the multiplexed signal 56 tothe mmWave power head 38 via the wired communication medium 54.

To help further understand the inner structure of the multiplicationpaths 60(1)-60(N) in the mmWave power head 38, FIG. 4 is discussed next.In this regard, FIG. 4 is a schematic diagram providing an exemplaryillustration of an inner structure of the multiplication paths60(1)-60(N) for generating the LO clock signals 44(1)-44(N) in themmWave power head 38 of FIG. 2. Common elements between FIGS. 2 and 4are shown therein with common element numbers and will not bere-described herein.

The mmWave power head 38 may include a signal shaping circuit 88 forshaping the pilot signal 42 from a sinusoidal shaped signal to a squareshaped signal to help ease the multiplications performed by the clockmultiplier 66 in each of the multiplication paths 60(1)-60(N). Notably,it is also possible to embed the signal shaping circuit 88 into each ofthe multiplication paths 60(1)-60(N).

With reference back to FIG. 2, the mmWave RF signal 49 may betransmitted from an antenna array 90 in an RF beam after being amplifiedby a power amplifier 92. To be able to form the RF beam from multipleantennas in the antenna array 90, it is necessary to provide multiplecopies of the mmWave RF signal 49 to the multiple antennas with phasecoherency. In this regard, FIG. 5 is a schematic diagram of the mmWavepower head 38 of FIG. 2 configured to support mmWave beamforming. Commonelements between FIGS. 2 and 5 are shown therein with common elementnumbers and will not be re-described herein. For the convenience ofillustration and reference, the multiplication path 60(1) is discussedherein as a non-limiting example of the selected multiplication path.Accordingly, the LO clock signal 44(1) generated by the multiplicationpath 60(1) is referenced herein as the selected LO clock signal 46 atthe selected LO reference frequency F_(LO). It should be appreciatedthat any of the multiplication paths 60(1)-60(N) in FIG. 2 can bedesignated as the selected multiplication path for providing theselected LO clock signal 46 to support mmWave beamforming.

The mmWave power head 38 includes a transmit phase shifter 94 coupled tothe selected multiplication path to receive the selected LO clock signal46 at the selected LO reference frequency F_(LO). The transmit phaseshifter 94 is controlled by a transmit phase control signal 96, whichmay be received in the control signal 70, to phase shift the selected LOclock signal 46 to generate a plurality of phase-coherent LO clocksignals 98(1)-98(M). The mixer circuit 48 in FIG. 2 may be replaced by aplurality of mixer circuits 100(1)-100(M). The mixer circuits100(1)-100(M) are coupled to the transmit phase shifter 94 to receivethe phase-coherent LO clock signals 98(1)-98(M). In addition, the mixercircuits 100(1)-100(M) are also configured to receive the communicationsignal 40 at the IF frequency F_(F). The mixer circuits 100(1)-100(M)are configured to upconvert the communication signal 40 based on thephase-coherent LO clock signals 98(1)-98(M) to generate a plurality ofphase-coherent mmWave RF signals 102(1)-102(M) at the mmWave carrierfrequency F_(C), respectively. The phase-coherent mmWave RF signals102(1)-102(M) are amplified by a plurality of power amplifiers104(1)-104(M) for transmission in a mmWave beam 106 from a plurality ofantennas 108(1)-108(M), respectively.

The antennas 108(1)-108(M) may also receive a plurality of mmWave RFsignals 110(1)-110(M), respectively. The mmWave RF signals 110(1)-110(M)may be amplified by a plurality of low-noise amplifiers (LNAs)112(1)-112(M), respectively. The mixer circuits 100(1)-100(M) may befurther configured to downconvert the mmWave RF signals 110(1)-110(M) toa plurality of phase-coherent received communication signals114(1)-114(M), respectively. The mmWave power head 38 may include areceive phase shifter 116 configured to generate a second communicationsignal 118. The receive phase shifter 116 may be controlled by a receivephase control signal 120, which can be received as part of the controlsignal 70. The mmWave power head 38 may further include a switch 122.The switch 122 can be switched to a position A to provide thecommunication signal 40 to the mixer circuits 100(1)-100(M), or beswitched to a position B to receive the second communication signal 118.

Notably, it is possible to include more than one of the mmWave powerhead 38 of FIG. 2 to support multiple mmWave RF front end subsystems. Inthis regard, FIG. 6 is a schematic diagram of an exemplary modem system124 configured to support multiple mmWave RF front end subsystems126(1)-126(4) by employing more than one of the mmWave power head 38 ofFIG. 2.

The modem system 124 includes a plurality of mmWave power heads128(1)-128(4) for providing a plurality of LO clock signals130(1)-130(4) to the mmWave RF front end subsystems 126(1)-126(4),respectively. Each of the mmWave power heads 128(1)-128(4) isfunctionally equivalent to the mmWave power head 38 of FIGS. 2, 4, and5. Although the modem system 124 is shown herein to include only themmWave RF front end subsystems 126(1)-126(4), it should be appreciatedthat more mmWave RF front end subsystems can be supported by addingadditional mmWave power heads.

The mmWave power heads 128(1)-128(4) are coupled to an RF basebandcircuit 132 via a plurality of wired communication mediums134(1)-134(4), respectively. Each of the wired communication mediums134(1)-134(4) can be a coaxial cable. Notably, each of the mmWave powerheads 128(1)-128(4) is coupled to the RF baseband circuit 132 by asingle wired communication medium.

The RF baseband circuit 132 includes a PLL frequency synthesizer 136configured to generate a plurality of pilot signals 138(1)-138(4). TheRF baseband circuit 132 includes a plurality of baseband circuits140(1)-140(4) for generating a plurality of communication signals142(1)-142(4), respectively. The communication signals 142(1)-142(4) aremultiplexed with the pilot signals 138(1)-138(4) to generate a pluralityof multiplexed signals 144(1)-144(4), respectively. The multiplexedsignals 144(1)-144(4) are communicated from the RF baseband circuit 132to the mmWave power heads 128(1)-128(4) via the wired communicationmediums 134(1)-134(4), respectively.

Notably, it is possible to include more than one of the modem system 124of FIG. 6 in a mmWave base station. In this regard, FIG. 7 is aschematic diagram of an exemplary base station 146 employing more thanone of the modem system 124 of FIG. 6.

As shown in FIG. 7, the base station 146 is configured to include eightmodem systems 148(1)-148(8). Each of the modem systems 148(1)-148(8) isfunctionally equivalent to the modem system 124 of FIG. 6. Although thebase station 146 as shown in FIG. 7 includes only the modem systems148(1)-148(8), it should be appreciated that the base station 146 can bescaled up or down to include more or less than the modem systems148(1)-148(8).

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present disclosure. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A millimeter wave (mmWave) power head comprising:a signal input coupled to a wired communication medium and configured toreceive a multiplexed signal comprising a communication signal at anintermediate frequency (IF) frequency and a pilot signal at a basefrequency; filter circuitry coupled to the signal input and configuredto demultiplex the multiplexed signal to separate the communicationsignal and the pilot signal; one or more multiplication paths configuredto multiply the pilot signal to generate one or more local oscillator(LO) clock signals at one or more harmonic frequencies relative to thebase frequency of the pilot signal, respectively; and at least one mixercircuit coupled to a selected multiplication path among the one or moremultiplication paths and configured to upconvert the communicationsignal from the IF frequency to an mmWave carrier frequency based on aselected LO clock signal generated by the selected multiplication path.2. The mmWave power head of claim 1 wherein the base frequency of thepilot signal is at least ten times higher than a crystal oscillator(XTAL) reference clock associated with a phase locked loop (PLL)frequency synthesizer.
 3. The mmWave power head of claim 1 furtherconfigured to receive a control signal at a frequency below threehundred megahertz via the wired communication medium.
 4. The mmWavepower head of claim 1 wherein the selected multiplication path isconfigured to generate the selected LO clock signal at a selected LOreference frequency higher than the mmWave carrier frequency to enable ahigh-side injection of the selected LO clock signal.
 5. The mmWave powerhead of claim 1 further comprising a transmit phase shifter coupled tothe selected multiplication path and a plurality of mixer circuitscoupled to the transmit phase shifter, wherein: the transmit phaseshifter is configured to phase shift the selected LO clock signalgenerated by the selected multiplication path to generate a plurality ofphase-coherent LO clock signals; and the plurality of mixer circuits isconfigured to upconvert the communication signal based on the pluralityof phase-coherent LO clock signals to generate a plurality ofphase-coherent mmWave RF signals at the mmWave carrier frequency,respectively.
 6. The mmWave power head of claim 5 wherein the pluralityof mixer circuits is coupled to a plurality of antennas configured totransmit the plurality of phase-coherent mmWave RF signals in an RFbeam.
 7. The mmWave power head of claim 1 wherein the filter circuitrycomprises: a first filter configured to pass the communication signal atthe IF frequency and reject the pilot signal at the base frequency; anda second filter configured to pass the pilot signal at the basefrequency and reject the communication signal at the IF frequency. 8.The mmWave power head of claim 7 wherein each of the first filter andthe second filter is an acoustic filter selected from the groupconsisting of: a surface acoustic wave (SAW) filter; a bulk acousticwave (BAW) filter; and a film bulk acoustic resonator (FBAR) filter. 9.The mmWave power head of claim 1 wherein each of the one or moremultiplication paths comprises: a clock multiplier configured tomultiply the pilot signal to generate a respective LO clock signal amongthe one or more LO clock signals at a respective harmonic frequencyamong the one or more harmonic frequencies; and a bandpass filterconfigured to pass the respective LO clock signal and reject noisesassociated with the respective LO clock signal.
 10. The mmWave powerhead of claim 9 wherein the bandpass filter in each of the one or moremultiplication paths is a transmission line filter.
 11. The mmWave powerhead of claim 1 wherein the at least one mixer circuit is furtherconfigured to downconvert the communication signal from the mmWavecarrier frequency to the IF frequency based on the selected LO clocksignal generated by the selected multiplication path.
 12. The mmWavepower head of claim 1 wherein the one or more multiplication pathscomprise at least two multiplication paths.
 13. A modem systemcomprising: a radio frequency (RF) baseband circuit; and a plurality ofmmWave power heads coupled to the RF baseband circuit via a plurality ofwired communication mediums, respectively; wherein each mmWave powerhead among the plurality of mmWave power heads comprises: a signal inputcoupled to a wired communication medium among the plurality of wiredcommunication mediums and configured to receive a multiplexed signalcomprising a communication signal at an intermediate frequency (IF)frequency and a pilot signal at a base frequency; filter circuitrycoupled to the signal input and configured to demultiplex themultiplexed signal to separate the communication signal and the pilotsignal; one or more multiplication paths configured to multiply thepilot signal to generate one or more local oscillator (LO) clock signalsat one or more harmonic frequencies relative to the base frequency ofthe pilot signal, respectively; and at least one mixer circuit coupledto a selected multiplication path among the one or more multiplicationpaths and configured to upconvert the communication signal from the IFfrequency to an mmWave carrier frequency based on a selected LO clocksignal generated by the selected multiplication path.
 14. The modemsystem of claim 13 wherein each mmWave power head among the plurality ofmmWave power heads is coupled to the RF baseband circuit via a singlecoaxial cable.
 15. The modem system of claim 13 wherein each mmWavepower head among the plurality of mmWave power heads further comprises atransmit phase shifter coupled to the selected multiplication path and aplurality of mixer circuits coupled to the transmit phase shifter,wherein: the transmit phase shifter is configured to phase shift theselected LO clock signal generated by the selected multiplication pathto generate a plurality of phase-coherent LO clock signals; and theplurality of mixer circuits is configured to upconvert the communicationsignal based on the plurality of phase-coherent LO clock signals togenerate a plurality of phase-coherent mmWave RF signals at the mmWavecarrier frequency, respectively.
 16. The modem system of claim 15wherein the plurality of mixer circuits is coupled to a plurality ofantennas configured to transmit the plurality of phase-coherent mmWaveRF signals in an RF beam.
 17. The modem system of claim 13 wherein thefilter circuitry comprises: a first filter configured to pass thecommunication signal at the IF frequency and reject the pilot signal atthe base frequency; and a second filter configured to pass the pilotsignal at the base frequency and reject the communication signal at theIF frequency.
 18. The modem system of claim 13 wherein each of the oneor more multiplication paths comprises: a clock multiplier configured tomultiply the pilot signal to generate a respective LO clock signal amongthe one or more LO clock signals at a respective harmonic frequencyamong the one or more harmonic frequencies; and a bandpass filterconfigured to pass the respective LO clock signal and reject noisesassociated with the respective LO clock signal.
 19. The modem system ofclaim 13 wherein the at least one mixer circuit is further configured todownconvert the communication signal from the mmWave carrier frequencyto the IF frequency based on the selected LO clock signal generated bythe selected multiplication path.
 20. The modem system of claim 13wherein for each of the plurality of mmWave power heads, the RF basebandcircuit is configured to: generate the pilot signal at the basefrequency that is at least ten times higher than a crystal oscillator(XTAL) reference frequency for a phase locked loop (PLL) frequencysynthesizer; multiplex the communication signal at the IF frequency andthe pilot signal at the base frequency to generate the multiplexedsignal; and provide the multiplexed signal to the mmWave power head overthe wired communication medium coupled to the mmWave power head amongthe plurality of wired communication mediums.